Human skin aging is a multifactorial and complex biological process affecting the different constituents of the skin. Skin aging is a combination of intrinsic or innate aging, and extrinsic aging (or photoaging) that results from exposure to environmental factors such as sunlight, pollutants, etc.
With age-skin volume, resilience, and pliability are decreased, at least in part due to altered patterns and levels of glycosaminoglycans (GAGs), especially hyaluronic acid (HA). Glycosaminoglycans and proteoglycans are abundant structural components of the extracellular matrix in addition to collagen fibers. HA forms large complexes that crosslink to other matrix proteins, such as collagen, resulting in the formation of supermolecular structures and functions to provide structure to the skin. HA has a unique capacity to bind and retain water molecules. Chemically, HA is composed of repeating polymeric disaccharides of D-glucuronic acid and N-acetyl-D-glucosamine linked by a glucuronidic β (1→3) bond. Unlike other GAGs, HA is not covalently linked to a protein core, but it may form aggregates with proteoglycans. HA polymers occur in a large number of configurations and shapes, depending on their size, salt concentration, pH, and associated cations.
In humans, HA is most abundant in the skin. The most dramatic histochemical change observed in senescent skin is the marked disappearance of epidermal HA. With increasing aging, a steady decline of HA occurs in the upper epidermal layer, with concomitant increases in the basal layer of the epidermis and the upper portions of the papillary dermis, while at senescence HA is entirely absent in the epidermis and present in the upper dermis. It is evident that during aging the epidermis loses the principal molecule responsible for binding and retaining water molecules, resulting in loss of skin moisture and accounting for some of the most striking alterations of the aged skin, including decreased structure, less support for microvessels, wrinkling, altered elasticity and loss of face volumes especially as regards to the lips.
The cosmetic formulation of the invention address specific needs of lip skin care.